1. Technical Field
The present invention generally relates to flexible printed circuit boards, and particularly, to a stiffener sheet and a stiffened flexible printed circuit board using the same.
2. Discussion of Related Art
With high demand of foldable electronic devices such as foldable mobile phones, flexible printed circuit boards (FPCBs) are widely employed for achieving electrical connection between movable part and main body. Generally, various kinds of electronic components (e.g. an integrated circuit) are mounted on FPCBs. However, strength of the FPCBs is not adequate for mounting such electronic components using the generally used surface mount technology (SMT).
In order to overcome above problem, referring to FIG. 1, a stiffener sheet 110 is attached to a surface of a flexible printed circuit board 130. An adhesive layer 120 is sandwiched between the stiffener sheet 110 and the flexible printed circuit board 130. In such circumstance, electronic components can be mounted on a portion of the flexible printed circuit board 130 corresponding to the stiffener sheet 110. However, if the stiffener sheet 110 and the flexible printed circuit board 130 have different thermal expansion coefficients, the stiffener sheet 110 and the flexible printed circuit board 130 may bend due to different thermal expansion, resulting in increase difficulty of mounting electronic components on bent flexible printed circuit boards 130.
What is needed, therefore, is a stiffener sheet has similar thermal expansion coefficient with flexible printed circuit boards, and a stiffened flexible printed circuit board including the same.